So what's the cause for the recent turnaround? Aftergood points to a May 2011 directive issued by Director of National Intelligence James Clapper:

That DNI directive appears to have broken the logjam of agency resistance, and at least some parts of the intelligence community that previously rebuffed GAO inquiries have become completely cooperative, congressional officials said.

POGO strongly supported an amendment to the Act that would have crystallized the GAO's authority to conduct oversight of the intelligence community. But the amendment disappeared from the final legislation without a trace, and in its place was the instruction to the DNI. We were skeptical that this would result in allowing Congress to fully assert its power, but it seems at least now there is some oversight, which we welcome.

At any rate, GAO’s increased involvement in oversight of the intel world is certainly welcome news. As Aftergood writes, this involvement can "expand the current capacity of intelligence oversight, bringing new resources to bear and increasing the likelihood that intelligence activities are carried out consistent with law and good policy."